Early signs of infection in Cacao swollen shoot virus (CSSV) inoculated cocoa seeds and the discovery of the cotyledons of the resultant plants as rich sources of CSSV

Despite the huge efforts and funds expended to try and bring Cacao swollen shoot virus (CSSV) disease under control, the disease has remained largely intractable. Inspired by the need to inject newideas into the current breeding programmes for CSSV resistance, the interactions between cocoa and the virus in CSSV-infected plants from 3 days post inoculation (dpi) to about 30 dpi were studied using both microscopic and molecular methods. Cellular modifications such as nucleic acid-rich inclusion bodies, apoptosis, and the in situ localisation of the virus in novel tissues that is cotyledons and hypocotyl, were discerned by microscopic examinations. These cellular modifications were observed incotyledons of seedlings as young as 8 dpi. By validating these microscopic results using PCR it was also discovered that the cotyledons of the inoculated plants were virus-rich. CSSV was amplified or detected in total DNAs extracted from all 4 CSSV-isolates studied, and in some cases the detection was from as early as 3dpi plants. Compared to cocoa leaves, the traditional source from which CSSV or its DNA is usually extracted, the cotyledons were much easier to process and analyse. The significance ofthese findings to the CSSV-resistant breeding programmes, and to CSSV research in general is discussed

Paleogene Radiation of a Plant Pathogenic Mushroom

Background: The global movement and speciation of fungal plant pathogens is important, especially because of the economic losses they cause and the ease with which they are able to spread across large areas. Understanding the biogeography and origin of these plant pathogens can provide insights regarding their dispersal and current day distribution. We tested the hypothesis of a Gondwanan origin of the plant pathogenic mushroom genus Armillaria and the currently accepted premise that vicariance accounts for the extant distribution of the species. Methods: The phylogeny of a selection of Armillaria species was reconstructed based on Maximum Parsimony (MP), Maximum Likelihood (ML) and Bayesian Inference (BI). A timeline was then placed on the divergence of lineages using a Bayesian relaxed molecular clock approach. Results: Phylogenetic analyses of sequenced data for three combined nuclear regions provided strong support for three major geographically defined clades: Holarctic, South American-Australasian and African. Molecular dating placed the initial radiation of the genus at 54 million years ago within the Early Paleogene, postdating the tectonic break-up of Gondwana. Conclusions: The distribution of extant Armillaria species is the result of ancient long-distance dispersal rather than vicariance due to continental drift. As these finding are contrary to most prior vicariance hypotheses for fungi, our result